Health informatics — Medical waveform format — Part 1: Encoding rules

This document specifies how medical waveforms, such as electrocardiogram, electroencephalogram, spirometry waveform, etc., are described for interoperability among healthcare information systems. This document can be used with other relevant protocols, such as HL7, DICOM®, the ISO/IEEE 11073 series, and database management systems for each purpose. This is a general specification, so specifications for particular waveform types and for harmonization with DICOM®, SCP-ECG, X73, etc. are not given. This document does not include lower layer protocols for message exchange. For example, a critical real-time application such as a patient monitoring system is out of scope and this is an implementation issue.

Informatique de santé — Format de la forme d'onde médicale — Partie 1: Règles d'encodage

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INTERNATIONAL ISO
STANDARD 22077-1
Second edition
2022-01
Health informatics — Medical
waveform format —
Part 1:
Encoding rules
Informatique de santé — Format de la forme d'onde médicale —
Partie 1: Règles d'encodage
Reference number
ISO 22077-1:2022(E)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO 22077-1:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 22077-1:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms, definitions and abbreviated terms .............................................................................................................................. 1

3.1 Terms and definitions ...................................................................................................................................................................... 1

3.2 Abbreviated terms .............................................................................................................................................................................. 2

4 Basic specifications ...........................................................................................................................................................................................2

4.1 Basic attributes ...................................................................................................................................................................................... 2

4.1.1 General ........................................................................................................................................................................................ 2

4.1.2 Sampling attributes ......................................................................................................................................................... 3

4.1.3 Frame attributes ...................................................................... ........................................................................................... 3

4.2 Encoding rule ........................................................................................................................................................................................... 4

4.2.1 General ........................................................................................................................................................................................ 4

4.2.2 Tag (T) ......................................................................................................................................................................................... 4

4.2.3 Data length (L) ...................................................................................................................................................................... 5

4.2.4 Value (V) .................................................................................................................................................................................... 6

4.3 Encoding principle .............................................................................................................................................................................. 6

4.3.1 General ........................................................................................................................................................................................ 6

4.3.2 Definition levels .................................................................................................................................................................. 6

4.3.3 General principles in interpretation, scope and priority of definitions ............................ 6

5 Basic rules (Level 1) .........................................................................................................................................................................................8

5.1 Primary description .......................................................................................................................................................................... 8

5.1.1 Sampling attributes ......................................................................................................................................................... 8

5.1.2 Frame attributes ...................................................................... ........................................................................................... 9

5.1.3 Waveform ............................................................................................................................................................................... 10

5.1.4 Channel .................................................................................................................................................................................... 13

5.2 Auxiliary rule ........................................................................................................................................................................................ 14

5.2.1 Data description ............................................................................................................................................................... 14

5.2.2 Other definition ................................................................................................................................................................ 16

5.2.3 Information description ........................................................................................................................................... 17

6 Supplemental description (Level 2) .............................................................................................................................................21

7 Extended description (Level 3) .........................................................................................................................................................24

Annex A (informative) MFER conformance statement ..................................................................................................................27

Annex B (informative) Description example ...........................................................................................................................................28

Annex C (informative) Event information description ..................................................................................................................35

Annex D (informative) Example of standard encoding.................................................................................................................36

Bibliography .............................................................................................................................................................................................................................41

iii
© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO’s adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 215, Health informatics.

This second edition cancels and replaces the first edition (ISO 22077-1:2015) of which it constitutes a

minor revision. The changes are as follows:
— some typographical errors have been corrected;
— Clause 2 “Normative references” has been added;

— Note 1 to entry has been added to terminology entries 3.1.1, 3.1.3 and 3.1.4, and terminology entry

3.1.5 has been added;
— classifications and types of waveform in Table 10 have been added;
— the character code in Table 39 has been changed;
— a Bibliography has been added.
A list of all parts in the ISO 22077 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
Introduction

Medical waveform data such as an electrocardiogram (ECG) or an electroencephalogram (EEG) are

widely utilized in physiological examinations, physiological research, electronic medical records,

healthcare information and other areas in the clinical field. Medical waveform data can be used for

many medical and research purposes if digital signal processing technology is applied to standardize

the data in a digital format. For medical waveforms, it is essential to standardize the data format to

expedite the mutual application of the standard so that the data can be processed electronically and

used in a variety of ways.

Simple and easy implementation: the application of medical waveform format encoding rules (MFER)

is very simple and is designed to facilitate understanding, easy installation, troubleshooting and low

implementation cost.

Harmonization with other standards: MFER are specially utilized to describe the medical waveform

data. Other information than waveform data, such as patient demographic data and finding information,

etc., should be written using other healthcare standards, e.g. HL7, DICOM® , the ISO/IEEE 11073 series.

In addition, experts in each field should independently develop relevant standards for medical

specifications, e.g. MFER for ECG is developed by cardiologists and EEG is developed by neurologists.

Combination with coded information and text information: MFER policy is that both machine and

human readable manner are used. Namely coded information is for computer processable and text

data are for human readable information. For example, arterial blood pressure (ART) is coded as 129

and information description fields indicate “right radial artery pressure”. As the description of MFER

is quite flexible, MFER neither hinders the features of each system nor impedes the development of

technologies.

1) DICOM is the trademark of a product supplied by Medical Imaging & Technology Alliance, a division of the

National Electrical Manufacturers Association. This information is given for the convenience of users of this

document and does not constitute an endorsement by ISO of the product named.
© ISO 2022 – All rights reserved
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INTERNATIONAL STANDARD ISO 22077-1:2022(E)
Health informatics — Medical waveform format —
Part 1:
Encoding rules
1 Scope

This document specifies how medical waveforms, such as electrocardiogram, electroencephalogram,

spirometry waveform, etc., are described for interoperability among healthcare information systems.

This document can be used with other relevant protocols, such as HL7, DICOM®, the ISO/IEEE 11073

series, and database management systems for each purpose.

This is a general specification, so specifications for particular waveform types and for harmonization

with DICOM®, SCP-ECG, X73, etc. are not given.

This document does not include lower layer protocols for message exchange. For example, a critical

real-time application such as a patient monitoring system is out of scope and this is an implementation

issue.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
frame

waveform (3.1.5) encoding unit consisting of data blocks, channels (3.1.4) and sequences

Note 1 to entry: The frame in this document is the same as waveform frame.
3.1.2
medical waveform

time sequential data that are sampled by an A/D converter or transmitted from medical equipment

3.1.3
sampling
data that are converted at a fixed time interval
Note 1 to entry: The sampling in this document is the same as waveform sampling.
© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
3.1.4
channel
individual waveform (3.1.5) data group
Note 1 to entry: The channel in this document is the same as waveform channel.
3.1.5
waveform
graph showing a change in some physical quantity with time
3.2 Abbreviated terms
A/D analogue to digital
ECG electrocardiogram
EEG electroencephalogram
GPS global positioning system
HL7 Health Level Seven
DICOM® Digital Imaging and Communications in Medicine
IEEE Institute of Electrical and Electronic Engineers
IEC International Electrotechnical Commission
JIS Japanese Industrial Standard
LSB least significant bit
MFER medical waveform format encoding rules
OID object identifier

SCP-ECG Standard Communications Protocol for Computerized Electrocardiography (see EN 1064)

SpO saturation of peripheral oxygen
UID unique identifier
UUID universally unique identifier
VCG vectorcardiogram
4 Basic specifications
4.1 Basic attributes
4.1.1 General

Medical waveform data described in accordance with the MFER consists of sampling attributes (see

Figure 1), frame attributes (see Figure 2) and other supplemental information.
© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
4.1.2 Sampling attributes
Sampling information has two attributes: sampling rate and sampling resolution.

a) Sampling rate is described with sampling interval or sampling frequency. The sampling interval

stands for the time or distance interval of each sampled data as distributed sampled waveform

data.

b) Sampling resolution represents a minimum sampling value per least significant bit (LSB).

Key
T sampling interval (or frequency)
R resolution
Figure 1 — Sampling attributes
4.1.3 Frame attributes

The frame is a waveform encoding unit consisting of data blocks, channels and sequences. A

configuration example of a frame is shown in Figure 2.
a) The data block is the waveform data array for each channel.

b) The channels indicate different waveform groups, e.g. if three waveform groups exist, the number

of channels is three.

c) The sequence represents the repetition of the group with the data block and channel.

© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
Key
1 frame
2 data block
3 channel
4 sequence
Figure 2 — Frame attributes
4.2 Encoding rule
4.2.1 General

The header and waveform data should be encoded based on the encoding rules, which are composed of

the tag, length and value (TLV), as shown in Figure 3.

— The tag (T) consists of one or more octets and indicates the attribute of the data value.

— The data length (L) is the length of data values indicated in one or more octets.

— The value (V) is the contents which are indicated by tag (T), e.g. attribute definition, waveform data.

Figure 3 — Data unit
4.2.2 Tag (T)

The tag is composed of a class, primitive/context (P/C) and tag number. The tag is classified into four

classes (see Table 1). Classes 0 to 2 are MFER standard coding and class 3 is for private use. The private

definition is intended for special purposes but should be included within any updated future version.

© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
Table 1 — Tag
8 7 6 5 4 3 2 1
Class P/C Tag number
0 0
0 1 MFER
0/1
1 0
1 1 Private
a) Primitive type (P/C = 0).
P/C = 0 indicates a primitive description.
b) Context type (P/C = 1).

This has only two tags, which are group and channel definition on current MFER. Figure 4 gives an

example of a group definition.
Figure 4 — Group definition
4.2.3 Data length (L)
4.2.3.1 General

The data length indicates the number of octets used for data values in the value (V) section (i.e. the

length excluding octets used for tag and data length sections). The data length encoding method differs

depending on whether the number of octets used for data are less than 127 or more than 128 octets.

4.2.3.2 When the data value section uses 127 octets or less
The length is encoded in one octet, as shown in Figure 5.
Figure 5 — Data length ≤ 127 octets
4.2.3.3 When the data value section uses 128 octets or more

The long data length can be encoded using multiple octets. The first octet indicates the number of

octets used to represent the total data length. For example, two subsequent octets are used to indicate

the waveform data length from 128 to 65 535 and thus three octets are used to encode the data length

as shown in Figure 6. However, MFER allow representation of a data length using multiple octets even if

the length is less than or equal to 127 octets. For example, four octets can describe up to 4 294 967 295

bytes length as a data part.
Figure 6 — Data length
© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
4.2.3.4 Designation of indefinite data length

MFER allow designation of an indefinite data length by encoding 80 h on the top of the data length field

(see Figure 7). The indefinite data length is valid only when the waveform data value is described at

the end of the file. This indefinite length designation is terminated by encoding the end-of-contents

(tag = 00, data length = 00).
Figure 7 — Indefinite length designation and end-of-contents designation
4.2.3.5 When the data length is 0

“Data length 0” indicates that the definition indicated by tag resets to the default value. Namely, on the

root definition, the concerned items re-initialize to default values, and in cases of the channel definition,

the channel definition is re-initialized to the root definition.
4.2.4 Value (V)

The header or waveform data values are encoded in the value section according to descriptors specified

by the tag.
4.3 Encoding principle
4.3.1 General

All definitions in MFER have default values, so any additional or amended definitions are optional.

Thus, the definition corresponding to each tag has a default value, so re-definition is not necessary if

the default value is retained. It is expected that default definitions will suffice for most purposes.

4.3.2 Definition levels
4.3.2.1 Level 1 — Basic definitions

Definitions at level 1 are basic definitions, which are ordinary rules (marked with an asterisk) and

ensure precise encoding.
4.3.2.2 Level 2 — Supplementary definitions

Definitions at level 2 are supplementary definitions. They may be used as required but it is desirable to

associate the supplementary definitions with a host protocol where they can be defined with the host

protocol.
4.3.2.3 Level 3 — Extended definitions

Definitions at level 3 are extended definitions, which should be used as little as possible. Items of these

extended definitions can considerably affect the system with regard to security. Thus, great care should

be taken when using them.
4.3.3 General principles in interpretation, scope and priority of definitions
4.3.3.1 Initial values (default value)

All definitions in MFER have initial values that are applied until redefined by any subsequent definition.

© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
4.3.3.2 Multiple definitions

Multiple definitions may be made for any item. Depending on the items, a new definition, an old

definition or all definitions (such as for events) can be used multiple times.

For example, setting the sampling frequency to 250 Hz overrides the initial value of 1 kHz.

If multiple events occur, they are interpreted in definition order.
4.3.3.3 Later definition priority

Each definition is interpreted in definition order. If an item has related definitions, definition should be

made in due order. The default endianity is big-endian, so to use little-endian endianity the definition

for little-endian must be designated.

For example, before defining each channel, the number of channels should be defined.

4.3.3.4 Channel attributes definition order

Before defining the attributes of a channel, the number of channels should be defined. If the number of

channels is defined later, previous channel definitions are reset to the root definition including default

values.

4.3.3.5 Root definition (general definition) and channel definition (definition per channel)

The root definition is effective for all channels. The channel definition is effective only for the relevant

channel and overrides the root definition. However, care should be taken because if a subsequent

change to the root definition is made it will override the default content of the relevant channel for

subsequent channel definitions.

For example, if EEG is designated in the root definition, ECG designated for a channel in the channel

definition overrides EEG.
4.3.3.6 Definition reset

If the data length is defined as zero (no data) in the definition of an item, the content in the definition

is reset to default value. If the data length is designated as zero in a channel definition, the definition

follows the root definition including the default value. If the number of channels is defined, contents

defined for the channel attribute are all reset to the root definition including the default value.

4.3.3.7 Incomplete definition ignored

If a definition is made without an adequate preceding definition, the definition is ignored.

In the absence of any complete definition, the default root definition will be applied.

For example, if the number of channels is undefined, any dependent channel definition is ignored.

4.3.3.8 Succession of definitions

Unless redefined, each definition applies to all succeeding frames in the effective range, except for the

data pointer which is succeeding renewed. Thus, contents defined in the root definition apply to all

frames unless overridden by channel definition(s), so it suffices to define common items in the root

definition.

For example, to use little-endian for all encodings with MFER, define little-endian once, then it is

effective over the whole region irrespective of frames.
© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
4.3.3.9 Definition and efficacy of data

It depends on the functional capability of the user application whether or not the user can use data

defined by the provider. If some content cannot be processed, users may discard all the data or use only

the processable range of data.
5 Basic rules (Level 1)
5.1 Primary description
5.1.1 Sampling attributes
5.1.1.1 General

Sampling attributes are sampling frequency or sampling interval and resolutions are given in Tables 2

to 5.
5.1.1.2 MWF_IVL (0Bh): Sampling rate

This tag indicates the frequency or interval the medical waveform is sampled (see Table 2).

Table 2 — Sampling rate
MWF_IVL* Data Default Encoding range/ Duplicated
length remarks definitions
Unit 1 —
th −128 +127
Exponent (10 power) 1 10 to 10
11 0Bh 1 000 Hz Override
Mantissa ≤ 4 e.g. unsigned 16-bit
integer

The unit may be frequency in Hertz, time in seconds or distance in meters (see Table 3).

Table 3 — Sampling rate unit
Unit Value Remarks
Frequency Hz 0 Including power
Time interval s 1 —
Distance m 2 —
5.1.1.3 MWF_SEN (0Ch): Sampling resolution

This tag indicates the resolution, minimum bits, the medical waveform is sampled (generally, digitized)

(see Table 4).
Table 4 — Sampling resolution
MWF_SEN* Data Default Encoding range/ Duplicated
length remarks definitions
Unit 1 —
−128 +127
10 to 10
Exponent (10 power) 1
12 0Ch See Table 5 Override
Mantissa ≤ 4 e.g. unsigned 16-bit
integer
© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
Table 5 — Sampling resolution units
Unit Value Default Remarks
Voltage V 0 0,000 001 V —
mm Hg(Torr) 1 — —
Pa 2 — —
Pressure
cm H O 3 — —
mm Hg/s 4 — —
dyne 5 — —
Force
N 6 — —
Ratio % 7 — Include volume fraction (%)
Temperature °C 8 — —
min 9 — —
Heart rate
−1 10 — —
Resistance Ω 11 — —
Current A 12 — —
Rotation r/min 13 — —
W 14 — —
Power
dB 15 — —
Mass kg 16 — —
Work J 17 — —
–2 –5
Vascular resistance dyne ⋅ s ⋅ m cm 18 — —
l 19 — —
Flow rate, flow, volume l/s 20 — —
l/min 21 — —
Luminous intensity cd 22 — —
5.1.2 Frame attributes
5.1.2.1 General

As described in Figure 2, a frame is composed of data blocks, channels and sequences.

5.1.2.2 MWF_BLK (04h): Data block length
This tag indicates the number of data sampled in a block (see Table 6).
Table 6 — Data block length
MWF_BLK* Data length Default Remarks Duplicated definitions
04 04h ≤ 4 1 — Override
5.1.2.3 MWF_CHN (05h): Number of channels

This tag indicates the number of channels (see Table 7). As the previously specified channel attribute

is reset to the root definition including default, the number of channels should be specified before

each definition of the channel attribute. The number of channels cannot be specified with a channel

definition of channel attribute.
© ISO 2022 – All rights reserved
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ISO 22077-1:2022(E)
Table 7 — Number of channels
MWF_CHN* Data length Default Remarks Duplicated definitions
05 05h ≤ 4 1 — Override
5.1.2.4 MWF_SEQ (06h): Number of sequences

This tag indicates the number of sequences (see Table 8). If the number of sequences is not designated,

it depends on the data block length, the number of channels and the number of waveform data values

which are defined for the concerned frame.
Table 8 — Number of sequences
MWF_SEQ* Data length Default Remarks Duplicated definitions
06 06h ≤ 4 Depends on waveform data length — Override
5.1.3 Waveform
5.1.3.1 General

The waveform type, waveform attributes, and waveform data are encoded as follows.

5.1.3.2 MWF_WFM (08h): Waveform class

Waveforms such as standard 12-lead ECG and monitoring ECG are grouped based on instruments and

purposes, as shown in Table 9.
Table 9 — Waveform class
MWF_WFM* Data length Default Remarks Duplicated definitions
2 0 (Unidentified) —
08 08h Override
2 < Str ≤ 32 Waveform description —

As a general rule, standardization will be made by type of waveforms, each is described in a separate

specification (e.g. for standard 12-lead ECG 11073-92301). However, because monitoring systems use

multiple waveforms such as ECG, SpO2, EEG, etc., refer to the specification for each individual waveform

standard.
For types of waveform (see
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 22077-1
ISO/TC 215
Health informatics — Medical
Secretariat: ANSI
waveform format —
Voting begins on:
2021-10-05
Part 1:
Voting terminates on:
Encoding rules
2021-11-30
Informatique de santé — Format de la forme d'onde médicale —
Partie 1: Règles d'encodage
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 22077-1:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2021
---------------------- Page: 1 ----------------------
ISO/FDIS 22077-1:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 22077-1:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms, definitions and abbreviated terms .............................................................................................................................. 1

3.1 Terms and definitions ...................................................................................................................................................................... 1

3.2 Abbreviated terms .............................................................................................................................................................................. 2

4 Basic specifications ...........................................................................................................................................................................................2

4.1 Basic attributes ...................................................................................................................................................................................... 2

4.1.1 General ........................................................................................................................................................................................ 2

4.1.2 Sampling attributes ......................................................................................................................................................... 3

4.1.3 Frame attributes ...................................................................... ........................................................................................... 3

4.2 Encoding rule ........................................................................................................................................................................................... 4

4.2.1 General ........................................................................................................................................................................................ 4

4.2.2 Tag (T) ......................................................................................................................................................................................... 4

4.2.3 Data length (L) ...................................................................................................................................................................... 5

4.2.4 Value (V) .................................................................................................................................................................................... 6

4.3 Encoding principle .............................................................................................................................................................................. 6

4.3.1 General ........................................................................................................................................................................................ 6

4.3.2 Definition levels .................................................................................................................................................................. 6

4.3.3 General principles in interpretation, scope and priority of definitions ............................ 6

5 Basic rules (Level 1) .........................................................................................................................................................................................8

5.1 Primary description .......................................................................................................................................................................... 8

5.1.1 Sampling attributes ......................................................................................................................................................... 8

5.1.2 Frame attributes ...................................................................... ........................................................................................... 9

5.1.3 Waveform ............................................................................................................................................................................... 10

5.1.4 Channel .................................................................................................................................................................................... 13

5.2 Auxiliary rule ........................................................................................................................................................................................ 14

5.2.1 Data description ............................................................................................................................................................... 14

5.2.2 Other definition ................................................................................................................................................................ 16

5.2.3 Information description ........................................................................................................................................... 17

6 Supplemental description (Level 2) .............................................................................................................................................21

7 Extended description (Level 3) .........................................................................................................................................................24

Annex A (informative) MFER conformance statement ..................................................................................................................27

Annex B (informative) Description example ...........................................................................................................................................28

Annex C (informative) Event information description ..................................................................................................................35

Annex D (informative) Example of standard encoding.................................................................................................................36

Bibliography .............................................................................................................................................................................................................................41

iii
© ISO 2021 – All rights reserved
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ISO/FDIS 22077-1:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

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electrotechnical standardization.

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described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

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www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 215, Health informatics.

This second edition cancels and replaces the first edition (ISO 22077-1:2015) of which it constitutes a

minor revision. The changes are as follows:
— some typographical errors have been corrected;
— Clause 2 “Normative references” has been added;

— Note 1 to entry has been added to terminology entries 3.1.1, 3.1.3 and 3.1.4, and terminology entry

3.1.5 has been added;
— classifications and types of waveform in Table 10 have been added;
— the character code in Table 39 has been changed;
— a Bibliography has been added.
A list of all parts in the ISO 22077 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
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ISO/FDIS 22077-1:2021(E)
Introduction

Medical waveform data such as an electrocardiogram (ECG) or an electroencephalogram (EEG) are

widely utilized in physiological examinations, physiological research, electronic medical records,

healthcare information and other areas in the clinical field. Medical waveform data can be used for

many medical and research purposes if digital signal processing technology is applied to standardize

the data in a digital format. For medical waveforms, it is essential to standardize the data format to

expedite the mutual application of the standard so that the data can be processed electronically and

used in a variety of ways.

Simple and easy implementation: the application of medical waveform format encoding rules (MFER)

is very simple and is designed to facilitate understanding, easy installation, troubleshooting and low

implementation cost.

Harmonization with other standards: MFER are specially utilized to describe the medical waveform

data. Other information than waveform data, such as patient demographic data and finding information,

etc., should be written using other healthcare standards, e.g. HL7, DICOM® , the ISO/IEEE 11073 series.

In addition, experts in each field should independently develop relevant standards for medical

specifications, e.g. MFER for ECG is developed by cardiologists and EEG is developed by neurologists.

Combination with coded information and text information: MFER policy is that both machine and

human readable manner are used. Namely coded information is for computer processable and text

data are for human readable information. For example, arterial blood pressure (ART) is coded as 129

and information description fields indicate “right radial artery pressure”. As the description of MFER

is quite flexible, MFER neither hinders the features of each system nor impedes the development of

technologies.

1) DICOM is the trademark of a product supplied by Medical Imaging & Technology Alliance, a division of the

National Electrical Manufacturers Association. This information is given for the convenience of users of this

document and does not constitute an endorsement by ISO.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 22077-1:2021(E)
Health informatics — Medical waveform format —
Part 1:
Encoding rules
1 Scope

This document specifies how medical waveforms, such as electrocardiogram, electroencephalogram,

spirometry waveform, etc., are described for interoperability among healthcare information systems.

This document can be used with other relevant protocols, such as HL7, DICOM®, the ISO/IEEE 11073

series, and database management systems for each purpose.

This is a general specification, so specifications for particular waveform types and for harmonization

with DICOM®, SCP-ECG, X73, etc. are not given.

This document does not include lower layer protocols for message exchange. For example, a critical real-

time application such as a patient monitoring system is out of scope and this is an implementation issue.

2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
frame

waveform (3.1.5) encoding unit consisting of data blocks, channels (3.1.4) and sequences

Note 1 to entry: The frame in this document is the same as waveform frame.
3.1.2
medical waveform

time sequential data that are sampled by an A/D converter or transmitted from medical equipment

3.1.3
sampling
data that are converted at a fixed time interval
Note 1 to entry: The sampling in this document is the same as waveform sampling.
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ISO/FDIS 22077-1:2021(E)
3.1.4
channel
individual waveform (3.1.5) data group
Note 1 to entry: The channel in this document is the same as waveform channel.
3.1.5
waveform
graph showing a change in some physical quantity with time
3.2 Abbreviated terms
A/D analogue to digital
ECG electrocardiogram
EEG electroencephalogram
GPS global positioning system
HL7 Health Level Seven
DICOM® Digital Imaging and Communications in Medicine
IEEE Institute of Electrical and Electronic Engineers
IEC International Electrotechnical Commission
JIS Japanese Industrial Standard
LSB least significant bit
MFER medical waveform format encoding rules
OID object identifier

SCP-ECG Standard Communications Protocol for Computerized Electrocardiography (see EN 1064)

SPO saturation of peripheral oxygen
UID unique identifier
UUID universally unique identifier
VCG vectorcardiogram
4 Basic specifications
4.1 Basic attributes
4.1.1 General

Medical waveform data described in accordance with the MFER consists of sampling attributes (see

Figure 1), frame attributes (see Figure 2) and other supplemental information.
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ISO/FDIS 22077-1:2021(E)
4.1.2 Sampling attributes
Sampling information has two attributes: sampling rate and sampling resolution.

a) Sampling rate is described with sampling interval or sampling frequency. The sampling interval

stands for the time or distance interval of each sampled data as distributed sampled waveform

data.

b) Sampling resolution represents a minimum sampling value per least significant bit (LSB).

Key
T sampling interval (or frequency)
R resolution
Figure 1 — Sampling attributes
4.1.3 Frame attributes

The frame is a waveform encoding unit consisting of data blocks, channels and sequences. A

configuration example of a frame is shown in Figure 2.
a) The data block is the waveform data array for each channel.

b) The channels indicate different waveform groups, e.g. if three waveform groups exist, the number

of channels is three.

c) The sequence represents the repetition of the group with the data block and channel.

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ISO/FDIS 22077-1:2021(E)
Key
1 frame
2 data block
3 channel
4 sequence
Figure 2 — Frame attributes
4.2 Encoding rule
4.2.1 General

The header and waveform data should be encoded based on the encoding rules, which are composed of

the tag, length and value (TLV), as shown in Figure 3.

— The tag (T) consists of one or more octets and indicates the attribute of the data value.

— The data length (L) is the length of data values indicated in one or more octets.

— The value (V) is the contents which are indicated by tag (T), e.g. attribute definition, waveform data.

Figure 3 — Data unit
4.2.2 Tag (T)

The tag is composed of a class, primitive/context (P/C) and tag number. The tag is classified into four

classes (see Table 1). Classes 0 to 2 are MFER standard coding and class 3 is for private use. The private

definition is intended for special purposes but should be included within any updated future version.

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ISO/FDIS 22077-1:2021(E)
Table 1 — Tag
8 7 6 5 4 3 2 1
Class P/C Tag number
0 0
0 1 MFER
0/1
1 0
1 1 Private
a) Primitive type (P/C = 0).
P/C = 0 indicates a primitive description.
b) Context type (P/C = 1).

This has only two tags, which are group and channel definition on current MFER. Figure 4 gives an

example of a group definition.
Figure 4 — Group definition
4.2.3 Data length (L)
4.2.3.1 General

The data length indicates the number of octets used for data values in the value (V) section (i.e. the

length excluding octets used for tag and data length sections). The data length encoding method differs

depending on whether the number of octets used for data are less than 127 or more than 128 octets.

4.2.3.2 When the data value section uses 127 octets or less
The length is encoded in one octet, as shown in Figure 5.
Figure 5 — Data length ≤ 127 octets
4.2.3.3 When the data value section uses 128 octets or more

The long data length can be encoded using multiple octets. The first octet indicates the number of

octets used to represent the total data length. For example, two subsequent octets are used to indicate

the waveform data length from 128 to 65 535 and thus three octets are used to encode the data length

as shown in Figure 6. However, MFER allow representation of a data length using multiple octets even if

the length is less than or equal to 127 octets. For example, four octets can describe up to 4 294 967 295

bytes length as a data part.
Figure 6 — Data length
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ISO/FDIS 22077-1:2021(E)
4.2.3.4 Designation of indefinite data length

MFER allow designation of an indefinite data length by encoding 80 h on the top of the data length field

(see Figure 7). The indefinite data length is valid only when the waveform data value is described at

the end of the file. This indefinite length designation is terminated by encoding the end-of-contents

(tag = 00, data length = 00).
Figure 7 — Indefinite length designation and end-of-contents designation
4.2.3.5 When the data length is 0

“Data length 0” indicates that the definition indicated by tag resets to the default value. Namely, on the

root definition, the concerned items re-initialize to default values, and in cases of the channel definition,

the channel definition is re-initialized to the root definition.
4.2.4 Value (V)

The header or waveform data values are encoded in the value section according to descriptors specified

by the tag.
4.3 Encoding principle
4.3.1 General

All definitions in MFER have default values, so any additional or amended definitions are optional.

Thus, the definition corresponding to each tag has a default value, so re-definition is not necessary if

the default value is retained. It is expected that default definitions will suffice for most purposes.

4.3.2 Definition levels
4.3.2.1 Level 1 — Basic definitions

Definitions at level 1 are basic definitions, which are ordinary rules (marked with an asterisk) and

ensure precise encoding.
4.3.2.2 Level 2 — Supplementary definitions

Definitions at level 2 are supplementary definitions. They may be used as required but it is desirable to

associate the supplementary definitions with a host protocol where they can be defined with the host

protocol.
4.3.2.3 Level 3 — Extended definitions

Definitions at level 3 are extended definitions, which should be used as little as possible. Items of these

extended definitions can considerably affect the system with regard to security. Thus, great care should

be taken when using them.
4.3.3 General principles in interpretation, scope and priority of definitions
4.3.3.1 Initial values (default value)

All definitions in MFER have initial values that are applied until redefined by any subsequent definition.

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4.3.3.2 Multiple definitions

Multiple definitions may be made for any item. Depending on the items, a new definition, an old

definition or all definitions (such as for events) can be used multiple times.

For example, setting the sampling frequency to 250 Hz overrides the initial value of 1 kHz.

If multiple events occur, they are interpreted in definition order.
4.3.3.3 Later definition priority

Each definition is interpreted in definition order. If an item has related definitions, definition should be

made in due order. The default endianity is big-endian, so to use little-endian endianity the definition

for little-endian must be designated.

For example, before defining each channel, the number of channels should be defined.

4.3.3.4 Channel attributes definition order

Before defining the attributes of a channel, the number of channels should be defined. If the number of

channels is defined later, previous channel definitions are reset to the root definition including default

values.

4.3.3.5 Root definition (general definition) and channel definition (definition per channel)

The root definition is effective for all channels. The channel definition is effective only for the relevant

channel and overrides the root definition. However, care should be taken because if a subsequent

change to the root definition is made it will override the default content of the relevant channel for

subsequent channel definitions.

For example, if EEG is designated in the root definition, ECG designated for a channel in the channel

definition overrides EEG.
4.3.3.6 Definition reset

If the data length is defined as zero (no data) in the definition of an item, the content in the definition

is reset to default value. If the data length is designated as zero in a channel definition, the definition

follows the root definition including the default value. If the number of channels is defined, contents

defined for the channel attribute are all reset to the root definition including the default value.

4.3.3.7 Incomplete definition ignored

If a definition is made without an adequate preceding definition, the definition is ignored.

In the absence of any complete definition, the default root definition will be applied.

For example, if the number of channels is undefined, any dependent channel definition is ignored.

4.3.3.8 Succession of definitions

Unless redefined, each definition applies to all succeeding frames in the effective range, except for the

data pointer which is succeeding renewed. Thus, contents defined in the root definition apply to all

frames unless overridden by channel definition(s), so it suffices to define common items in the root

definition.

For example, to use little-endian for all encodings with MFER, define little-endian once, then it is

effective over the whole region irrespective of frames.
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ISO/FDIS 22077-1:2021(E)
4.3.3.9 Definition and efficacy of data

It depends on the functional capability of the user application whether or not the user can use data

defined by the provider. If some content cannot be processed, users may discard all the data or use only

the processable range of data.
5 Basic rules (Level 1)
5.1 Primary description
5.1.1 Sampling attributes
5.1.1.1 General

Sampling attributes are sampling frequency or sampling interval and resolutions are given in Tables 2

to 5.
5.1.1.2 MWF_IVL (0Bh): Sampling rate

This tag indicates the frequency or interval the medical waveform is sampled (see Table 2).

Table 2 — Sampling rate
MWF_IVL* Data Default Encoding range/ Duplicated
length remarks definitions
Unit 1 —
th −128 +127
Exponent (10 power) 1 10 to 10
11 0Bh 1 000 Hz Override
Mantissa ≤ 4 e.g. unsigned 16-bit
integer

The unit may be frequency in Hertz, time in seconds or distance in meters (see Table 3).

Table 3 — Sampling rate unit
Unit Value Remarks
Frequency Hz 0 Including power
Time interval s 1 —
Distance m 2 —
5.1.1.3 MWF_SEN (0Ch): Sampling resolution

This tag indicates the resolution, minimum bits, the medical waveform is sampled (generally, digitized)

(see Table 4).
Table 4 — Sampling resolution
MWF_SEN* Data Default Encoding range/ Duplicated
length remarks definitions
Unit 1 —
th −128 +127
Exponent (10 power) 1 10 to 10
12 0Ch See Table 5 Override
Mantissa ≤ 4 e.g. unsigned 16-bit
integer
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ISO/FDIS 22077-1:2021(E)
Table 5 — Sampling resolution units
Unit Value Default Remarks
Voltage V 0 0,000 001 V —
mm Hg(Torr) 1 — —
Pa 2 — —
Pressure
cm H O 3 — —
mm Hg/s 4 — —
dyne 5 — —
Force
N 6 — —
Ratio % 7 — Include volume fraction (%)
Temperature °C 8 — —
min 9 — —
Heart rate
−1 10 — —
Resistance Ω 11 — —
Current A 12 — —
Rotation r/min 13 — —
W 14 — —
Power
dB 15 — —
Mass kg 16 — —
Work J 17 — —
–2 –5
Vascular resistance dyne ⋅ s ⋅ m cm 18 — —
l 19 — —
Flow rate, flow, volume l/s 20 — —
l/min 21 — —
Luminous intensity cd 22 — —
5.1.2 Frame attributes
5.1.2.1 General

As described in Figure 2, a frame is composed of data blocks, channels and sequences.

5.1.2.2 MWF_BLK (04h): Data block length
This tag indicates the number of data sampled in a block (see Table 6).
Table 6 — Data block length
MWF_BLK* Data length Default Remarks Duplicated definitions
04 04h ≤ 4 1 — Override
5.1.2.3 MWF_CHN (05h): Number of channels

This tag indicates the number of channels (see Table 7). As the previously specified channel attribute

is reset to the root definition including default, the number of channels should be specified before

each definition of the channel attribute. The number of channels cannot be specified with a channel

definition of channel attribute.
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Table 7 — Number of channels
MWF_CHN* Data length Default Remarks Duplicated definitions
05 05h ≤ 4 1 — Override
5.1.2.4 MWF_SEQ (06h): Number of sequences

This tag indicates the number of sequences (see Table 8). If the number of sequences is not designated,

it depends on the data block length, the number of channels and the number of waveform data values

which are defined for the concerned frame.
Table 8 — Number of sequences
MWF_SEQ* Data length Default Remarks Duplicated definitions
06 06h ≤ 4 Depends on waveform data length — Override
5.1.3 Waveform
5.1.3.1 General

The waveform type, waveform attributes, and waveform data are encoded as follows.

5.1.3.2 MWF_WFM (08h): Waveform c
...

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